Attention and Change Blindness in Visual Search Experiments

1. Computational VisionCSCI 363, Fall 2018Lecture 24Attention and Change Blindness(why you shouldn't text while driving)

2. Project Presentations You will be graded on the following: Content Presentation Style Structure

3. Content You have some latitude as to what you present for your project, but you must include the following: • Introduction -- What is your topic/question? Why did you choose it? • Background -- Describe the problem you are addressing. What are the important questions about this problem that need to be addressed? What is the basic theory underlying the problem? • Main result -- Describe the main experiments or theories that you researched. What is the scientific data that supports the theories? How do the results relate to the main problem? • Conclusion -- What can we conclude about the problem?

4. Presentation Style How you present is at least (if not more) important than what you present. You need to focus on: • Making eye contact with the audience • Speaking clearly and audibly • Keeping a calm demeanor (at least appear to be calm) • Pacing the talk well • Giving the talk while standing (Don't sit!)

5. Visual Attention • Only the region in the center of the retinal image is seen in detail. • Visual attention limits the region of the scene processed.

6. Where's Waldo? If we are looking for something in the scene, we must shift our attention around the scene to find it.

7. Visual Search Experiments • We can study how people move their attention around using visual search experiments. • Subjects are asked to look for a target figure among distractors. • They must respond as quickly as possible saying whether or not the target is present. • Their reaction time is measured. • The number of items in the scene is varied.

8. Example 1: Find the Blue Square

9. Example 1: Find the Blue Square

10. Example 2: Find the B

11. Example 2: Find the B

12. Example 3: Find the O

13. Example 4: Find the Orange Square

14. Inefficient Reaction time Efficient Number of items Two types of search Efficient Search: As the number of distractors increases, the reaction time stays the same. (e.g. blue square among red squares). Inefficient Search: As the number of distractors increases, the reaction time increases.

15. What this tells us • Inefficient searches show that we are not aware of everything in the entire scene at the same time. • We constantly shift our gaze and our attention to look at different parts of the scene and examine them in detail. • We think we see the scene in detail, but we don't.

16. Change Blindness during Eye movements • We are constantly making rapid eye movements, known as saccades, as we scan a scene. • Vision is suppressed during saccades. • People fail to notice large changes in the scene if the change occurs during a saccade. (McConkie, Grimes, Ballard and others). • People also fail to notice large changes in the scene if they occur during a brief disruption (e.g. short blank period). • This is known as change blindness. (Rensink et al., 1996) • Demo (view with Firefox): http://www2.psych.ubc.ca/~rensink/flicker/download/

17. Movie Cuts can also cause Change Blindness A cut between scenes can also induce change blindness. Simons and Levin showed this in a series of experiments. Can you detect the changes? Conversation Movie

18. Change Blindness for Attended Objects Change blindness occurs even for objects that are the center of attention: Demo: Person answering phone

19. Change Blindness in Real Life Situations Disruptions in real life can also lead to change blindness: The door study

20. What's Going On? • What causes change blindness? • We don't see the entire scene in detail. • Only attended regions get into short term memory. • Attention is not enough. • We must intentionally process details in order to detect the changes.

21. Limits of attention Task: Count the number of passes made by the white team: Counting basketball passes

22. Cell Phone Use Makes it Worse Task: Count the number of times a disk crosses the white line. Event: Large item slowly drifts across the field during one of the trials. (Visible for 5 seconds). Result (no cell phone): 30% fail to notice the cross. Result (with cell phone): 90% fail to notice the cross. Scholl, B. J., Noles, N. S., Pasheva, V., & Sussman, R. (2003) Journal of Vision

23. Other Effects of Cell phone use People talking on cell phones while driving... • are more likely to miss traffic signals. • react more slowly to traffic signals when they see them. • don't detect changes in real world traffic scenes as well. • react more slowly to vehicles braking in front of them. These are all equally true for hands-free devices. Listening to the radio does not have the same effect. Sources: Strayer & Johnston (2001) Psychological Science Strayer et al. (2003) J. Exp. Psych. Applied

24. Don't even think about texting while driving! Boston Globe, Sunday July 5, 2009 Car and Driver conducted a test of texting while driving. Condition RT (35 mph) RT(70 mph) Sober and attentive 0.51 sec 0.48 sec Drunk (BAC .08) 0.55 sec 0.55 sec Reading a Text 1.00 sec 0.71 sec Writing a Text 0.94 sec 0.86 sec In the texting condition at 70 mph, the car traveled an average of 40 extra feet before the driver hit the brake pedal. Texting while driving is significantly worse than driving while drunk.